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Old 04-14-2018, 10:03 PM   #1
masterdrago
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Pin Weight

On the spec page for the 2018 3791RD Montana, the hitch weight shows 2,835#. I'm assuming that is dry empty. What would be considered overloaded on hitch/pin? When we had ours weighed recently, the gross was 15,100 with pin at 3,100. I'm just wondering at what point my front basement and genny room will become too heavy.
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Old 04-14-2018, 10:30 PM   #2
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My 2015 3790RD weighed 16,600 lbs with a pin weight of 3,800 lbs when loaded for an extended trip to the Yukon and Alaska.
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Old 04-15-2018, 05:15 AM   #3
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I would say it depends on your tow vehicle.
What's the payload on your tow vehicle?
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Old 04-15-2018, 07:00 AM   #4
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With the pin at 3,100# and the truck loaded to travel (full fuel, firewood, extra fuel, hitch, and other crap along with two occupants), the margin is 2,800#. This is what more could be loaded onto the hitch in the rear of the truck. What I'm more interested in is if anyone knows where the weight of the pin of the trailer becomes excessive? At what point are we overloading the frame? If one considers the standard guidelines, going over 25% of trailer gross (in this case, 4,250#) is the line. I'm just wanting to know what others have read or discovered. Using the spec data on the Keystone web pages, it looks as if they are using empty weight and a 20% guideline -- 2,835pin=13,900empty (x) 20%. Everyone I've seem post their real pin is far above that # in spec data.
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Old 04-15-2018, 07:05 AM   #5
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Here's the thing with the Rear Den models, you conceivably (no you can) put pretty much all the heavy stuff in the rear storage areas and if required put light stuff up front thereby keeping the pin weight right in around where it is spec'd by the company. I know that is how mine is loaded, it tows great (always have about 1/3 in fresh water tank when travelling) as well. There is so much storage in the rear storage compartments it begs the question why you would load up the truck which usually leads to the ride getting bouncy.. In regard to pin weights it usually comes down to it is what it is however these rear den models allow you to adjust for best ride...... Just sayin
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Old 04-15-2018, 07:07 AM   #6
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BTW you will in all likely hood over load the tires long before you will ever overload the frame of your truck regardless of whether it is a 2500 or 3500 ....
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Old 04-15-2018, 07:52 AM   #7
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Masterdrago, as it stands it is not very clear how Keystone comes up with its published trailer GVWR. It seems to be unloaded trailer pin weight plus the axle ratings or the tire ratings whichever is lower. Broken frames at the pin are a known phenomenon and comparatively rare, but when they occur it is almost always the result of being overloaded at that point. some of that overloading can come from weight in the trailer and some can come from acceleration loads when the rig hits bumps or dips in the road. The other instances of such an occurance is poor construction. I have seen more than my share of broken trailer frames in or around the kingpin on the trailer. Invariably the primary reason is abusing the frame by exceeding it's design specs.

I'd use 25% of the 3791RD's OEM axle ratings as a better guide. So 2 x 7000lb axles = 14000 lb. At 25% that would be 3500 lb maximum pin or whatever your available remaining payload for your tow vehicle whichever is less. With no changes to the trailer frame or suspension or tires I would not exceed the GVWR of the trailer in any case. Using 25% of the trailer GVWR could lull one into putting more weight on the nose than might be considered safe. 4250 lbs seems high, to me, for the construction techniques used by Lippert when building Montana frames. Beyond 3500lbs (in this instance) I would be start to be uncomfortable about overloading the trailer frame at that location or the truck frame. But that's just me. I'd also invest in an air-cushioned hitch or air-ride pinbox to soften those acceleration forces especially if I was anything over 3000 lbs pin weight. Again, that's just me. Others may disagree and use different criteria and they may be perfectly viable, but there is no clear cut direction from Keystone in this area... unfortunately. Bottom line be safe.
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Old 04-15-2018, 09:40 AM   #8
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Here's the thing with the Rear Den models, you conceivably (no you can) put pretty much all the heavy stuff in the rear storage areas and if required put light stuff up front thereby keeping the pin weight right in around where it is spec'd by the company. I know that is how mine is loaded, it tows great (always have about 1/3 in fresh water tank when travelling) as well. There is so much storage in the rear storage compartments it begs the question why you would load up the truck which usually leads to the ride getting bouncy.. In regard to pin weights it usually comes down to it is what it is however these rear den models allow you to adjust for best ride...... Just sayin
Be extremely careful if you try this. Overload the rear and you will have tail wag and unit will become very unstable and dangerous. I trucked for 20 years and have seen it many times.
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Old 04-15-2018, 09:45 AM   #9
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Our rear basement is loaded with the giant bulky mostly light weight "stuff".


I've put some heavy containers in the genny room


The front basement has had all of the really heavy tools moved against the rear wall starboard side to counter the kitchen weight on the port rear tire. All the tires have near 1,000# margin except kitchen (700#). All this was rearranged after the first weigh in by RVSEF http://rvsafety.com/
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Old 04-15-2018, 09:47 AM   #10
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Quote "Be extremely careful if you try this. Overload the rear and you will have tail wag and unit will become very unstable and dangerous. I trucked for 20 years and have seen it many times"
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Ya so of I but try over 30yrs... I've had our 3790RD for almost 3yrs now and logged thousands of miles with it loaded as described, it tows best as I describe, no issues, handles perfect. You are stating otherwise but I'm guessing without actually ever towing a 3790 or 3791. On regular ball hitch pull trailers I totally agree with your statements however these units are from from that, the axles are rearward, and as I say it tows great, even better with a full tank of water however I don't like paying fuel mileage for a full tank when I won't need it. The on board water is there in case of an unplanned breakdown only.... Cheers
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Old 04-15-2018, 11:14 AM   #11
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I have a theory. If you put MORE weight on the pin, it should reduce the frame stress, right? That would place more weight almost on top of the truck, so the frame welded area shouldn't have so much force on it. Am I way off here?
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Old 04-15-2018, 11:16 AM   #12
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Be extremely careful if you try this. Overload the rear and you will have tail wag and unit will become very unstable and dangerous. I trucked for 20 years and have seen it many times.
I agree with this! As you know the 3790/3791 is an exception to the rule. Just about every fiver has a medium to large front storage basement, so it must be anticipated that most of the weight is allocated to that area. Of course any scenario of overloading is a possibility, so common sense comes into play. I think I read somewhere that the rear tray is rated at about 800 lbs., but I can't say where I saw that. Balancing is the key in every case.
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Old 04-15-2018, 02:29 PM   #13
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Hopefully I don't ramble here. Since I first started RVing in 2003, every towing guide I have ever read states 15 - 25% of trailer weight. Those stated percentages are to allow for safe acceleration, towing and braking of the tow vehicle and trailer combo.


Not enough pin weight means not enough weight on the tow vehicles drive axle. The tow vehicle will be trying to pull more weight with less traction. Less traction affects acceleration and braking. Ever notice how a dually rides and brakes smoother with weight in the bed ? At least mine does.


Too much pin weight stresses the tow vehicles suspension. It also takes weight off of the tow vehicles steering axle. The front end starts feel like its wandering. Not what you want in an emergency situation. Less weight on the steering axle also affects braking. The larger brakes are on the front and with less traction on the front, less braking power. Now you are hoping the rear brakes, with overloaded axles will stop your truck and rig.


Do the math according to your tow vehicles weight ratings. GVWR, GCWR, Cargo Capacity. If your truck has a GVWR of 14,000lbs and the actual weight, loaded for a trip, weighs 9,000lbs, then you have 5,000lbs remaining Cargo Capacity. The 14,000lbs is the max weight at which your truck can be safely driven. The 15 - 25% pin weight puts enough weight over the trucks rear axle to allow your truck to be safely driven pulling 12,000 - 14,000lbs behind.


The numbers you provided appear to be fine. (although you did not provide truck ratings) As long as you NEVER exceed your trucks GVWR and GCWR and your RVs GVWR, you will never be in trouble with a 25% pin weight. Do remember that the more weight you add to the front storage, the higher the pin weight. DON'T exceed your maximums. Redistribute or carry less.

BTW, most of the folks here that post their weights seem to be in the 20 - 22% pin weight range.


Now with all that being said, if you are actually asking how many pounds is too much for the front part of the RV frame...I'd say "when the floor collapses".
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Old 04-15-2018, 02:46 PM   #14
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Quote:
Originally Posted by speedster100 View Post
Quote "Be extremely careful if you try this. Overload the rear and you will have tail wag and unit will become very unstable and dangerous. I trucked for 20 years and have seen it many times"
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Ya so of I but try over 30yrs... I've had our 3790RD for almost 3yrs now and logged thousands of miles with it loaded as described, it tows best as I describe, no issues, handles perfect. You are stating otherwise but I'm guessing without actually ever towing a 3790 or 3791. On regular ball hitch pull trailers I totally agree with your statements however these units are from from that, the axles are rearward, and as I say it tows great, even better with a full tank of water however I don't like paying fuel mileage for a full tank when I won't need it. The on board water is there in case of an unplanned breakdown only.... Cheers
If you had checked my signature you would see what I have and tow. I'm glad you have been able to get away with this but do not think you should advise someone with less experience (possibly) to try it. Check out You Tube videos of trailer related wrecks. I for one don't want anyone getting hurt on my conscience.
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Old 04-15-2018, 03:36 PM   #15
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I know what happens if the rear of a trailer is overloaded ! What I said is that the rear den's don't have that issue. Don't make this something different, the question was in regard specifically to the Rear Den models and also it was about weight on the truck frame and had nothing to do with handling.

As I indicated if they are worried about it put the weight in the rear den storage of the RD as they can handle it and this is based on EXPERIENCE WITH THE REAR DEN MODEL...

Nuff said ........pay attention son !
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Old 04-15-2018, 04:09 PM   #16
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WeBeFulltime vs speedster100 battle royale.
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Old 04-15-2018, 07:40 PM   #17
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Okay, so if my GVWR for 5r is 16,800 and I like to stay around 20%, I can have a pin of 3,360. Sound right? My pin in Dec. was 3,100. I've since rearranged stuff and added stuff to take some weight off left & right rear, moving and adding to genny room and front basement. I've most like ly added about 300# midway between the pin and front axle. So if my math is right, I added ~150 to pin. Still under the 3,360. War on folks ---
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Old 04-15-2018, 08:20 PM   #18
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Okay, so if my GVWR for 5r is 16,800 and I like to stay around 20%, I can have a pin of 3,360. Sound right? My pin in Dec. was 3,100. I've since rearranged stuff and added stuff to take some weight off left & right rear, moving and adding to genny room and front basement. I've most like ly added about 300# midway between the pin and front axle. So if my math is right, I added ~150 to pin. Still under the 3,360. War on folks ---
Remember, your pin weight is a percentage of your LOADED trailer weight not the GVWR. If your rig actually weighs 16,800, you could go as high as 4,200lbs pin weight (assuming your truck has the cargo capacity).
The only way to know for sure is to know your trucks GVWR, your trucks actual weight, remaining available Cargo Capacity of the truck and your RVs actual weight. Trip to the scales.
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Old 04-16-2018, 06:17 AM   #19
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I know what happens if the rear of a trailer is overloaded ! What I said is that the rear den's don't have that issue. Don't make this something different, the question was in regard specifically to the Rear Den models and also it was about weight on the truck frame and had nothing to do with handling.

As I indicated if they are worried about it put the weight in the rear den storage of the RD as they can handle it and this is based on EXPERIENCE WITH THE REAR DEN MODEL...

Nuff said ........pay attention son !
Oh I realize now that you have the old model that doesn't have the large area with the pull-out tray that CAN be loaded to the point of being too heavy. Too much weight on rear is too much weight. Doesn't matter if that area is a "den" or a kitchen, BR, etc. But what does this kid know? I only logged 3 million SAFE miles.
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Old 04-16-2018, 06:56 AM   #20
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Oh I realize now that you have the old model that doesn't have the large area with the pull-out tray that CAN be loaded to the point of being too heavy. Too much weight on rear is too much weight. Doesn't matter if that area is a "den" or a kitchen, BR, etc. But what does this kid know? I only logged 3 million SAFE miles.
Right you are. Many may be too heavy and not know it.
My weight capacity has never and hopefully will never be an issue. hitch vertical towing weight = 5,000 lb, truck rear axle GVWR = 9,750 lb, and after having weighed in December, it looks like my rear truck margin is 2,800 lb. So yes, I could load a lot more crap in the RV and add over 1,000 lb to the pin and still be in spec. I'm just wondering why I'm seeing a fair number of posts that have broken frame/pin welds and if these folks are over or imbalanced loaded. It's possible that some of these failures might have been preventable. I've even considered taking the outside TV out so crap could be stowed there (there's room for a couple of cases of canned drinks or shorty bottled water) and it's right over the front axle. That would help balance the kitchen side higher weight. We don't full time (yet) and I think I have all the tools and other "stuff" loaded now.

One other note. Looking at my weighing record, I see that my trailer rear axle weight margin is ~800 lb. We had very little in the slide out rear storage in December. Some suggested moving some stuff to that area. That would simply force the rear trailer axle to get closer to the 7,000 lb max rating. Especially if the added stuff is way out near the back. My goal is to stay safe and inside limits. I suspect that many folks, especially new to dragging a 5r, do not get their trailers weighed. I know I'm preaching to the choir here but all should read good info at http://rvsafety.com/
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